Readers of my blog know that I took Fosamax 70 mg once
weekly for six calendar months (28 weeks) before the side effects forced me to
stop taking it. I waited one month and then began taking strontium citrate
daily. I now believe my initial treatment with the bisphosphonate, although lasting
only half a year, may have initially delayed and blunted my response to the
strontium. My DXA scores after six months on Fosamax and 18 months on strontium
were good but not stellar. Having now been on strontium for more than six years,
I have overcome any initial blunting, as shown by my most recent DXA scores,
which were terrific.
“A recent study
provides evidence that prior bisphosphonate therapy results in blunting and
delay of the BMD response to strontium ranelate. In a prospective study in
postmenopausal women with osteoporosis, 56 bisphosphonate-naïve women and 52
women treated with an oral bisphosphonate for at least one year, who had
stopped bisphosphonate therapy within the last month, were given strontium
ranelate 2 g daily, together with calcium and vitamin D supplements. After one
year of treatment, BMD in the lumbar spine had increased 5.6% in
bisphophonate-naïve women and by 2.1% in women previously treated with bisphosphonates;
at both six and 12 months the BMD increase in the former group was
significantly less than in the latter. At the total hip there was no
significant change in BMD at one year in the bisphosphonate-pretreated women
compared to an increase of 3.4% in the treatment-naïve group. In an extension
of this study, it was shown that BMD in the spine in pretreated women increased
in parallel with treatment naïve women from six months onwards, whereas some
blunting of the BMD response at the hip was still observed after two years of
treatment. The most likely mechanism to
explain these effects is that bisphosphonates inhibit the uptake of strontium
into bone because of suppression of bone turnover and the consequent reduction
in newly formed bone.”
“Osteoporosis: Diagnosis and Management,” Dale W. Stovall
(ed.), Chapter 13, pages 202-203.
